Liquid crystal element, phase modulation device, and control method of liquid crystal element

A phase modulation device comprising:

• an image data generator configured to generate image data corresponding to a distribution of phase change amount or a distribution of phase velocity based on information data;
• a controller configured to generate a gradation control signal based on the image data;
• and
• a liquid crystal element that is controlled by the gradation control signal, wherein
• the liquid crystal element comprises:
• a first substrate that includes a pixel region in which a plurality of pixel electrodes are arranged and one pixel electrode constitutes one pixel;
• a second substrate that includes a counter electrode facing the plurality of pixel electrodes and is arranged with a predetermined gap from the first substrate;
• liquid crystals filled in the predetermined gap;
• and
• a light receiver that is arranged in the vicinity of the pixel region on the first substrate and photoelectrically converts light with which the pixel region is irradiated to generate a light reception signal,
• an inclination angle of a wavefront of the light with which the pixel region is irradiated is changed by applying different driving voltages to the plurality of pixel electrodes based on a gradation control signal including gradation data corresponding to each pixel,
• the phase modulation device further comprises a light reception signal detector configured to generate a drive control signal for switching a driving state of the liquid crystal element from normal operation to a standby state or switching from the standby state to the normal operation, based on the light reception signal, and
• the controller controls the liquid crystal element to switch the driving state of the liquid crystal element from the normal operation to the standby state, or to switch from the standby state to the normal operation, based on the drive control signal.

A control method of a liquid crystal element, the method comprising:

• generating a light reception signal by photoelectrically converting light with which a pixel region, in which a plurality of pixel electrodes are arranged, one pixel electrode constitutes one pixel, and different driving voltages are applied to the plurality of pixel electrodes based on a gradation control signal including gradation data corresponding to each pixel, is irradiated;
• determining whether or not a signal level of the light reception signal is equal to or higher than a threshold voltage;
• when it is determined that the signal level of the light reception signal is not equal to or higher than the threshold voltage, determining whether or not a predetermined time or more has elapsed in the state that is not equal to or higher than the threshold voltage;
• and
• when it is determined that the predetermined time or more has elapsed, switching a driving state of the liquid crystal element from normal operation to a standby state.